1. Field of the Invention
This invention relates generally to electrical switches, and more particularly to micro-machined, electrostatically actuated switches of a type that can be fabricated on integrated circuit substrates using integrated circuit processing technology.
2. Description of the Related Art
With high density integrated circuits, power, size and space constraints are of primary importance. For example, because of their size, semiconductor switches have been fabricated on dielectric substrates of integrated circuit wafers. Since semiconductor switches have electrical resistance, they create a power loss in the switched signal which, with very low energy levels signals, can create a significant challenge to the circuit designers. For example, raising the power level of the signal can apply an additional heat loading to the circuit and must be removed.
Alternatively, electro-mechanical switches do have a low resistance, and thus, do not create a significant power loss in the switched signal. However, to date such switches have typically been quite large relative to the size of integrated circuit chips. For example, many of the switches can be the same size as the chip or even larger. Moreover, because of their size, the switches were typically located off of the chip surface. Thus, there has been a significant increase in the space requirements for the circuitry, resulting in a reduction in the overall circuit density. Furthermore, these electro-mechanical switches have their own relatively significant power requirements.
In addition, for microwave, millimeter wave and high data rate signal processing, the distances that the transmitted signal has to travel from the integrated circuit chip to the off wafer switch and back to the chip can result in a significant time delay in the signal that must be accounted for by the circuit designer.
With the advent of micro-machining, it has been shown that it is feasible to fabricate mechanical and electro-mechanical devices using thin film integrated circuit technology. Some specific examples are the levers, gears, sliders, and springs referred to in U.S. Pat. No. 4,740,410, issued on Apr. 26, 1988, to R. S. Muller, et al, and entitled Micro Mechanical Elements and Methods for their Fabrication. In addition, electro-mechanical devices such as rotatable motors and linear motors have been shown in U.S. Pat. No. 4,754,185, issued on Jun. 28, 1988 to K. J. Gabriel et al, and entitled Micro-Electrostatic Motor.